Grip



Feb. 23, 1965 R. c. CAVANAUGH 3,170,322

GRIP

Filed June 5, 1962 Filed June 5, 1962, Ser. No. 200,201 1 Claim. (Cl..73'-103) This invention 'relatesto grip useful inmaterials testing.

One object of thepresent invention is to provide such a grip in which the forces exerted on a specimen held in the grip may be effectively multiplied with respect to the input actuating forces, in an amount which may be predetermined over a very wide range. Other objects are to provide sucha grip in which jaws move-together transversely against opposed sides of a specimen free from any component of movement longitudinally of the specimen; in which each opposed jaw face is at all times the same distance from a plane including the centerline of a specimen in testing position; in which each jaw face is at United States Patent ,7 3,170,322 Patented Feb. 23, 1965 the lower surface of the piston portion of the'actuator. Held in the closure 48 against-vertical movement relative thereto by pin 58 is mounting element 60 which includes hole mounting 62 the center of which is on the vertical centerline 32. Air pressure may be selectively admitted through hose connection 64 andholes 66 and 68 into the zone 70 above the actuator36 and into the cylinder portion of the housing 10, to drive the actuator downwardly with a force determined by the product of the air pressure and the area-of the topsurface 74 of the actuator.

The lower ends of axially movable (axially of themselves, of course; not of the grip as a whole) links 24 all times maintained with its points for contacting a specimen defining planes parallel to said plane including the ing and opposed pairs of wedging or camming surfaces on an axially movable actuator, a corresponding pair of links with endsbiased against the camming surfaces centerline of a specimen in testing position; and which for movement by the actuator, and a corresponding pair A of intermediately pivotally mounted links secured at corresponding ends to the first-mentioned links and at opposed corresponding ends to a pair of oppositely coaxially movable jaw carriers.

Other objects, features and advantages will appear from the following description of a preferred embodiment of the invention, in conjunction with the attached drawings thereof, in which:

FIG. 1 is a side elevational view, partially in section, of said preferred embodiment; and

FIG. 2 is an end elevation thereof.

Referring now to the drawings, there is shown a frame 18 which includes an upper cylinder portion 12 and lower leg portions 14. The leg portions,14 each include slots 16, which are interrupted toward their lower ends by widened portions defining jaw-carrier bearings 18 square in cross-section, and toward their upper ends by widened portions defining slanted holes 20 in which are carried bearings 22 for axially movable links 24. The

, upper ends of the links 24 carry rollers 26 mounted rotataupper piston portion 38 of the actuator 36 includes a a groove in which is seated ring gasket 48 which provides a seal between said piston portion and the cylinder portion 12 of frame 10. The frame 10 includes a reversely directed annular portion 44 supporting actuator bearing 46.. Mounted on top of the frame and interiorly depending thereinto is closure 48, with ring gasket 50 mounted in the annular space therebetween in a groove around dependent portion 154thereof for sealing purposes. The actuator 36 is yieldingly urged at all times toward the closure 48, and held thereagainst when the actuator is not actuated, by spring 56 extending from the frame to include therethrough pins 76. which extend also through upper holes 78 0f intermediately pivotally mounted (on pins 80 secured in the frame 10) links 82 containing .toward their lower ends holes 84. Theholes 76' and84 are elongated in a direction longitudinal of the link 82 to accommodate the vertical movement relative to ea ch other of the outer ends of the links 24 and the jaw car riers 86, the latter of' which carry pins 88 passing through the elongated holes 84. The jaw carriers 86. are square in cross-section and movable in horizontal bearing 18, so that they are given horizontal non-rotating movement toward each other in use. Each carrier 86 includes a slot 90, said slots being oppositely directed and one being ro-' tated 90 from the other. Each slot carries shank 92 of a jaw 94, held in place by a pin 96. The jaws 94 and their faces 98 (which may be smooth or knurled or toothed, but which in any event are substantially verticallyplanar areas defined by and constituting the locus of all the specimen-engaging jaw extremities, whether the latter are for example tips of teeth or points on smooth surfaces) are at all times equidistant from centerline 32. The lower ends of pivotally mounted links 8-2 are outwardly urged by leaf springs 100 resting against the inner surfaces of slots 16.

In operation, air under pressure is introduced through floating piston action. The wedging surfaces 34 thereupon force apart sliding links 24, the rollers 26 rolling along the wedging surfaces. The pivoted links 82 are thereby rotated about pins 80 to drive together the jaw carriers 86 and jaws 94.

In the embodiment shown, the pin 80 is equidistant between the holes 78 and 84, so that the force exerted on each jaw carrier 86 through its pin 88 is substantially equal to the horizontal component of the force exerted by the sliding links 24 on the upper ends of the links 82. An advantage of the invention is that it provides for mov-' ing the pin about which the pivotally mounted link is mounted closer to either the upper or lower end of the pivotally mounted jlink,.to respectively produce either greater movement and less force in the jaw carriers and jaws or less movement and greater force in the jaw carriers and jaws. The relationship between force exerted on the actuatorand force exerted at (and movement of) the jaws may be advantageously varied alsoby altering the angle the wedging surfaces define with a vertical plane through centerline 32 parallel with the faces 98.

crease relative to actuator force, and, of course, the reverse.

angle for a portion of their extent and then at another angle, to vary jaw force and movement at different stages 7 continuous change in the movement-force relationship If desired, the wedging surfaces may be at one" between the actuator and theja'ws. The expression cam surfaces is used herein to include both planar wedging surfaces and non-planar cam surfaces.- If desired, the actuator may be driven mechanically, as by a screw or toggle, rather than by air pressure. The use of air pressure provides the advantages-of jaw follow-up and constant gripping forces even though specimen thickness diminishes during a test; of facilitating delicate and accurately regulated gripping of-fragile or sensitive specimens; and increasedcontrol of rate of jaw opening and closing.

Leaf springs 100 operating on links 82 drive the jaws away from each other when air pressure is released,spring 56 driving the actuator outward to override its jaw-closing,

action. Thus a specimen may be removed and another inserted. c

Other embodiments Within the invention and the appended claim will occur to those skilled in the art.

Iclaim: I

A grip comprising a frame with an upper cylinder portion, a pair of dependent leg portions, and a reversely directed portion extending upwardly into said cylinder portion, an actuator mounted in said cylinder portion for slidable movement axailly of said grip Within said reversely directed portion, said actuator including an upper piston portion for cooperation with said cylinder portion to be driven therealong by air pressure thereabove and a pair of wedging surfaces defining equal acute angles with the axis of said grip, a closure above said piston portion and secured in sealed relation to said frame, a mounting element secured in said closure and extending thereabove, said mounting element and said closure including cooperating passages for air under pressure, spring means cooperating with said frame and biasing said piston portion toward said closure, a first pair of links mounted for slidable movement in said frame, each said link being slidable axially of itself and in a direction perpendicular to one of said wedging surfaces; a roller rotatably mounted in the inner end of each of said first pair of links and engaging one of said Wedging surfaces, a second pair of links eachhaving. its upper end pivotally secured to an outer end of one of said first pair of links and being pivotally mounted intermediately of itself in said frame, a pair of jaw carriers mounted for coaxial slidable movement only in said frame in opposite directions along a line' perpendicular to said axis of said grip, each said jaw carrier being pivotally joined at an outer end to a lower end of one of said second pair of links, a pair of jaws with faces parallel toeach other and to the grip axis, and springmeans cooperating with said frame and biasing outwardly the lower ends of said second pair of links. 7

References (Iited in the file of this patent UNITED STATES PATENTS 

